A 10-year review of isoniazid-resistant TB management in Uzbekistan 2009-2020

SUMMARY BACKGROUND Isoniazid (INH, H) resistance is the most common drug-resistant TB pattern, with treatment success rates lower than those in drug-susceptible TB. The WHO recommends a 6-month regimen of rifampicin (RIF, R), ethambutol (EMB, E), pyrazinamide (PZA, Z), and levofloxacin (Lfx) (6REZLfx) for INH-resistant, RIF-susceptible TB (HRRS-TB). Uzbekistan has a high burden of TB (62/100,000 population) and multidrug-resistant TB (12/100,000 population). METHODS We conducted a retrospective, descriptive study of microbiologically confirmed HRRS-TB using routinely collected programmatic data from 2009 to 2020. RESULTS We included 854 HRRS-TB cases. Treatment success was 80.2% overall. For REZLfx, the treatment success rate was 92.0% over a short treatment duration, with no amplifications to RIF or second-line anti-TB drug resistance. We documented 46 regimens with REZLfx plus linezolid (success 87.0%) and 539 regimens using kanamycin or capreomycin (success 76.6%). We identified 37 treatment failures (4.3%), 30 deaths (3.5%), 25 resistance amplifications (2.9%), including eight to RIF (0.9%), and 99 lost to follow-up (LTFU) cases (11.6%). Unsuccessful outcomes were more common with older age, diabetes, chest X-ray cavities, smear positivity, smear-positive persistence, and male sex. LTFU was more common with injection-containing regimens. CONCLUSIONS REZLfx is a safe and effective first-line treatment for INH-resistant, RIF-susceptible TB. Treatment success was lower and LTFU was higher for injection-containing regimens.


Isoniazid (INH, H) resistance in Mycobacterium tuberculosis (MTB
) is likely a natural phenomenon due to frequent spontaneous mutations, especially at codon 315 of the katG gene resulting in moderateto high-level resistance and the c-15t mutation in the inhA promoter region resulting in low-level resistance. 1,2INH resistance is the most common TB resistance pattern, accounting for over 1 million new cases annually. 3,4Furthermore, INH monoresistance is the most common TB monoresistance pattern. 5,6NH-resistant, rifampicin (RIF, R) susceptible TB (H R R S -TB) includes strains susceptible and resistant to other first-line drugs, i.e., INH-monoresistant and polydrug-resistant TB (PDR-TB), respectively.However, first-line susceptibility results are often incomplete in H R R S -TB cases, except for INH and RIF.The global average annual incidence of H R R S -TB among all TB cases from 2002 to 2016 was 8.5% (95% confidence interval [CI] 7.4-9.7)overall, 7.3% (95% CI 6.1-8.6) for new cases, and 14.0% (95% CI 12-17)  for previously treated cases.7 H R R S -TB incidence is increasing among persons incarcerated or homeless.5,[8][9][10] The global prioritised use of Xpert ® MTB/Rif assays (Cepheid, Sunnyvale, CA, USA) means that RIFsusceptible TB cases are usually treated for drugsusceptible TB (DS-TB) without INH resistance testing, resulting in RIF monotherapy during the continuation phase for INH resistance cases.3,11 Treatment success with INH resistance is often poor compared with DS-TB, with success rates of 61.0-85.0%3,4,6 and more frequent adverse events.4 Failure rates range from 0.0-45.0%and mortality from 1.9% to 14.2%.3,4,6 Poor outcomes are associated with HIV co-infection, 3,6 longer treatment duration, 12 streptomycin use, 12 age, 6 male sex, 3,6 previous TB treatment, 12 cavitary disease, 12 smear positivity, 4 and smear-positive persistence.12 Historically, H R R S -TB treatment regimens were not standardised, 3,11 and access to drug susceptibility testing (DST) was limited, often focusing on RIF-resistant TB (RR-TB).3,13 The choice of regimen commonly depended on the previous treatment history and provider preference, often including a fluoroquinolone (FQ) and/or an aminoglycoside for 9-12 months.11,12 In 2018, the WHO issued new treatment recommendations for H R R S -TB, replacing 9 months of RIF, ethambutol (EMB, E), and pyrazinamide (PZA, Z) with 6 months of REZ plus levofloxacin (Lfx).11,12 The WHO supports the addition of high-dose INH for strains with inhA but not katG mutations.12 Globally, 64.3-78.6% of observed phenotypic INH resistance is associated with katG315 mutations alone, 6.8-19.2%with inhA-15 mutations alone, and 14.6% with both.14,15 The WHO European region, including Uzbekistan, has high rates of H R R S -TB, INH resistance, and katG315 mutations.14,15 One study identified katG315 mutations in 94% of INH-resistant isolates in six ex-Soviet states, including Kazakhstan, which borders Karakalpakstan.14 H R R S -TB treatment can result in acquired resistance to RIF and second-line TB drugs.Acquired RIF resistance occurred in 44/1,160 (3.8%) H R R S -TB patients not treated with FQs and 1/221 (0.5%) treated with FQs in one review.12 Because of this changing landscape, reviews of H R R S -TB treatment outcomes within long-running, comprehensive programmes are important in overall TB management.

Objectives
Our primary objective was to describe H R R S -TB treatment outcomes.Our secondary objectives were to 1) evaluate risk factors for unfavourable outcomes, 2) delineate treatment outcomes vis-a-vis treatment duration, 3) determine culture conversion rates, and 4) document frequencies of INH mutations.

Study design
This is a retrospective, observational study of microbiologically confirmed H R R S -TB cases in Karakalpakstan, Uzbekistan, using routinely collected programmatic data.

Setting
Karakalpakstan is an autonomous republic in northwestern Uzbekistan (land area 166,600 km 2 , population 1.88 million) with 16 rayons (districts) and one city, Nukus, the capital, where Médecins Sans Frontières (MSF) supports a centralised laboratory allowing for standardised, high-quality data.MSF has worked with the Ministry of Health (MOH) to strengthen TB diagnosis and treatment since 1998, using locally developed guidelines based on WHO recommendations.In 2009, MSF started supporting MOH drug-resistant TB (DR-TB) management in four rayons, expanding to all rayons and including drugsusceptible TB (DS-TB) by 2020.Approximately three-quarters of DR-TB and half of DS-TB cases were enrolled in an MSF-supported programme by 2020.
Karakalpakstan TB guidelines include management and follow-up by a multidisciplinary team (doctors, nurses, and social and mental health workers), social support, ancillary drugs for side effects, selfadministered therapy (SAT) for stable patients on injection-free, first-line regimens, and directly observed treatment (DOT) for complicated patients and those on injection-containing and/or second-line regimens.Monthly bacteriologic monitoring of positive TB cultures and a 2-year follow-up for relapse are recommended.
Treatment regimens and regimen changes are decided by a medical advisory committee of local TB experts, the TB Consilium.They review each case and prescribe treatment based on national TB treatment guidelines.Although clinical judgement is involved, they operate within the national guidelines, and all patients are treated within the national programme.Therefore, most H R R S -TB patients are started on similar treatment.From 2009 to 2018, the recommended treatment for H R R S -TB was REZ for 9 months.The recommendation was changed to REZLfx for 6 months in 2019.
MSF support focuses on health education, adherence counselling, and help with patients who have treatment challenges via phone calls, home visits, and counselling during clinic visits.All patients diagnosed with TB and initiated on treatment in an MSFsupported rayon are eligible for MSF support.

Participants
All patients testing positive for TB at the MSF-supported Republican Center of Tuberculosis and Pulmonology Hospital Laboratory (Nukus, Karakalpakstan, Uzbekistan) from March 2009 through December 2020 and enrolled in an MSF-supported programme were eligible.We have no detailed data on non-enrolled patients.We defined H R R S -TB as TB cases with bacteriologic results confirming phenotypic or genotypic INH resistance and RIF susceptibility without known resistance to second-line TB drugs.We excluded unenrolled patients and/or those with a positive Xpert MTB/Rif assay only.

Definitions
We used WHO definitions for H R R S -TB, previous treatment, smear-positive persistence, culture conversion/ reversion, transferred-out, and treatment outcomes. 16We defined amplified resistance as H R R S -TB cases that failed treatment and were found to be resistant to RIF and/or second-line anti-TB drugs.

Data sources and measurements
Epidemiological TB data in Karakalpakstan were collected by the MOH and MSF and transferred to Epi Info (Centers for Disease Control and Prevention, Atlanta, USA).Only study-relevant data were recorded, and access was restricted to the investigators. The

Quantitative analysis and statistical methods
We report descriptive analyses of baseline characteristics, interim responses, and end-of-treatment outcomes.For treatment outcome rates, the entire cohort was used as the denominator.v 2 statistics with Yates correction were used with one degree of freedom and a 0.05 significance level.

Ethical considerations
This study fulfilled the exemption criteria set by the MSF Ethics Review Board for a posteriori analyses of routinely collected clinical data and did not require MSF ERB review.This study was conducted with permission from the MSF Operational Centre Amsterdam, The Netherlands.

RESULTS
Of the 11,760 potentially eligible participants, we included 854 enrolled H R R S -TB cases.Table 1 shows their baseline characteristics.Most were male (55.7%), smear-positive (62.9%), with a history of TB treatment (62.3%), and with a history of INH exposure (51.3%).
Compared with all H R R S -TB patients, a higher proportion of the 99 LTFU patients took an injectable agent (79.8% vs. 63.7%) and were persistently smearpositive (18.2% vs. 7.2%).Injection-free regimens were protective against loss to follow-up (20.0%injection-free LTFU vs. 79.8%injection-containing LTFU).We found no relationship to the year of diagnosis or to rural vs. city residence.We have no information on measures for patient support of individual LTFU cases.

Secondary objective 2: Treatment outcomes vis-à-vis treatment duration
We have treatment durations on 98.7% of patients (843/854) (Table 2).The median duration for cured and completed patients was 10.1 months.The durations were shorter for injection-free regimens, especially REZLfx (6.6 months).The median duration to failure was 6.1 months, failure with amplification 5.1 months, death 4.2 months, and LTFU 4.4 months.

Drug side effects
Drug side effects were uncommon, mild, and frequently associated with PZA (37/89 episodes, 41.6%).Twelve patients on EMB (recommended dosage 15-20 mg/kg/day) experienced ophthalmologic side effects, six on PZA developed hepatitis, and two on RIF or CPM had decreased creatinine clearance.

DISCUSSION
We found a high treatment success rate of 92.0% (23/25)  with one LTFU, one death, and no amplified resistance in a small, select group treated with �6REZLfx alone for a Our overall treatment success rate was comparable to others (80.2% vs. 77.2-83.0%). 3,19,21,224][25][26][27] In Karakalpakstan, DS-TB treatment success from 2017 to 2020 was 80.5% (5,582/ 6,931) (personal communication, K. J. Kudaybergenov, Director, MOH of the Republic of Karakalpakstan).H R R S -TB treatment success was not worse than local DS-TB cases (80.2% vs. 80.5%), potentially due to MSF support for H R R S -TB patients.
We documented 539 H R R S -TB patients treated with KM or CPM.The WHO guidelines state that there are no data on these injectable agents in H R R S -TB treatment. 12We found a lower treatment success rate with injection-containing versus injection-free regimens (76.8% vs. 85.5%) and a higher frequency of LTFUs (79.8% vs. 20.0%).Our results support recommendations to phase out injection-containing regimens. 3,17,28e documented a small, select cohort of 46 patients treated with REZLfxLzd alone.Only one case was found in the literature. 18The treatment success (87.0%) and median treatment duration (9.4 months) were similar to those of REZ alone.

Side effects
We confirmed that PZA is the drug most often implicated in side effects. 4,28,29eatment durations Our treatment durations should be viewed with caution because these were usually determined by the standard of care.Nonetheless, the shortest median durations were for injection-free regimens, especially �6REZLfx (6.6 months).

Study limitations
Our study has some limitations.A complete record is missing for some patients.The study team collected variables such as sputum results and treatment outcomes according to existing documentation without independent review.We did not routinely document second-line anti-TB drug susceptibility before treatment.However, amplified resistance was uncommon.Not all laboratory-diagnosed TB isolates were tested for INH resistance for operational reasons, e.g., previous algorithms excluded direct Hain for smear-scanty cases and COVID-related laboratory shortages.Because of MSF support, our results may not be transferrable to cohorts where the support provided is not adequate.

CONCLUSIONS
H R R S -TB treatment success was high overall.�6REZLfx alone had the highest success over the shortest duration; however, the numbers were too small to draw conclusions.Injection-containing regimens were less successful and more likely to result in loss to follow-up.TB programmes should increase their capacity to detect H R R S -TB, and universal INH screening should be a global goal.
Figure shows the testing algorithm used in the MSF-supported Karakalpakstan Mycolab BSL3 Laboratory for INH resistance.The use of the pDST BD BACTEC� MGIT� 960 SIRE kit with the BACTEC MGIT 960 (BD, Franklin Lakes, NJ, USA) at an INH drug critical concentration of 1.0 mg/L started in 2005.INH resistance was also identified using the MTBDRplus v2.0 line-probe assay to detect mutations in the katG and inhA genes beginning in 2010.Annual external quality assessment is provided by the WHO Supranational Reference Laboratory in Gauting, Germany.Batch testing for the SIRE drug kit and the MTBDRplus kit used the sensitive control strain H37Rv and a known resistant strain.Because of algorithm changes and inconclusive results, not all 2009-2020 H R R S -TB cases had susceptibility results for all first-line drugs other than INH and RIF.Routine katG and inhA testing began in 2017, and second-line testing for resistance was initiated in 2019.